This invention relates to a method of determining the surface atomic layer of a solid sample by a reflection high energy electron diffraction (RHEED) method combined with (TRAXS) total reflection angle X-ray spectroscopy.
In the conventional RHEED method, the characteristic X-rays emitted from a surface of a sample when an electron beam is impinged thereon are detected to determine the elements constituting the surface of the sample. One problem of the RHEED method is a low measurement sensitivity attributed to the low intensity of the characteristic X-rays.
JP-A-60-82840 discloses RHEED/TRAXS analysis method in which, as shown in FIG. 9, the characteristic X-rays (fluorescent X-rays) Cx emitted from a surface of a sample 15 excited by an electron beam Ei with an incident angle .alpha. from an electron gun 16 are detected by a detector 17 at the total reflection angle .beta.. This method is advantageous because of a high detection sensitivity but has a problem because the X-ray penetration depth is not sufficiently small (30-50 .ANG.) and because the analysis is unable to perform when the surface to be detected is not smooth.
More particularly, when the conventional RHEED/TRAXS analysis is adopted to, for example, a (100) plane of a perovskite crystal of ABO.sub.3 in which the atomic layer containing the element A and the atomic layer containing the element B are alternately stacked, not only the outermost atomic layer but also the inner adjacent layer are simultaneously energized with the electron beam, so that it is impossible to identify the outermost atomic layer. In order to minimize the penetration depth as small as possible, therefore, it is necessary to set the incident angle .alpha. at about 0.1-1 radian. In this case, when the sample has a rough surface, it is impossible to obtain the critical angle for total reflection at positions as shown in FIG. 10.